1. Field of the Invention
The present invention relates to air flow indicators and more particularly to a device for measuring human breath inhalation flow rates. The present invention also relates to inhalation devices which provide an incentive to improve lung capacity and to exercise respiratory musculature. Particularly with patients experiencing post surgical pain, and inactive, obese, and geriatric patients, it is sometimes necessary to utilize a program of breathing exercise to maintain or increase the patient's lung capacity. Due to patient medication or lethargy, it has been found that an exerciser with incentive capabilities produces the best results. One type of incentive device is an air flow rate indicator which shows the patient he is performing his exercises correctly.
2. Description of the Prior Art
The prior art U.S. Pat. No. 4,060,074 depicts an incentive breathing device wherein several vertical air flow columns stand proximate each other. Each air flow column has an air intake orifice that opens directly to the atmosphere, a uniform cross-sectional area throughout its length, an air flow rate indicator located therein, and an air outlet that opens to an air duct which is in pneumatic communication with each of the other columns and with an air inhalation means. The user inhales through the air inhalation means and thereby withdraws air from all of the columns simultaneously. As inhaled air flows through all columns at an increasing rate, an air flow rate indicator rises to the top of a column at a precalibrated air inhalation rate to indicate the air flow rate that is being achieved. The indicator, upon rising to the top of the chamber, seals the air outlet for that chamber. As the flow rate of inhaled air continues to increase, indicators in the remaining columns will then sequentially rise to the tops of their columns and each column will be sealed except the last.
The air flow rate indicators are typcially lightweight spheres of slightly smaller outer diameter than the inner diameter of the column within which they reside. The gap between the sphere and the column wall is the parameter which is varied to calibrate the device, and a column for measuring high flow rates would have a larger gap, than a column for measuring low flow rates. It is the flow rate of air which is drawn through the column that causes the flow indicator to rise in the moving air to the top of the column and seal the air outlet at the top of the column.
Several problems have been found with this prior art device which the present invention overcomes. The problems exist because the top common air duct services all columns, each of which has an air intake orifice. Upon initial use, this construction results in the total air flow being shared through all columns, and it thus requires a substantial total air flow rate before the air flow rate in a single column is sufficient to lift a first sphere. Experience has shown that a minimum gap of approximately 40 thousandths of an inch (0.1 centimeters) is required to insure that a sphere will not become hung up in its column. This minimum gap is described in the preferred embodiment of the prior art, and its use results in a minimum air flow rate for the prior art of approximately 600 cubic centimeters per second. As the gap cannot be decreased, it is therefore the case that the prior art is unable to measure air flow rates that are below approximately 600 cubic centimeters per second. The prior art has attempted to circumvent this low air flow rate design limitation by making provision for the tilting of the device from its normal vertical orientation; however this solution is obviously less satisfactory than the new configuration of the present invention.
Significantly, low air flow rates of 150-500 cubic centimeters per second have been found to be the most beneficial to seriously afflicted users as they result in a laminar type of air flow to the user's lungs, and it is believed that laminar air flow causes better air exchange in the lungs. Thus, the prior art device is not configured to measure the type of air flow required by those who are most seriously in need of an incentive inhalation device, and a tilting of the device from its normal vertical orientation must be accomplished to attempt such a measurement.
The above-mentioned problems are overcome by the present invention. Low flow rates are easily obtainable through the utilization of the single air flow column. There is but a single air intake orifice, and thus all of the inhaled air must pass through each calibrated segment of the air flow column. There is no inhaled air that bypasses the low rate air flow indicator to undermine its accuracy, and a large range of air flow rates is easily obtained by the stacking of several differently calibrated air flow column segments to comprise the single air flow column. The ability to provide low flow rates for the user results in the user being able to obtain the laminar flow characteristics that have been found to be most desirable.
Further advantages of the present invention will become apparent when the preferred embodiment of the present invention is considered in conjunction with the accompanying drawings.